It is different, actually. If you have an iPhone/iPod/iPad, you have two options: install apps from Apple's app store, or jailbreak your phone and get your apps "black market" style. It's as if you had bought a lawnmower at Sears and now you can only buy fuel for it at Sears, or in the black market.
Yeah yeah you can get an Android, I know (I do have an Android). The thing is, as a developer, if you want to enter the mobile app market today, your app has to run on iOS. And it's a lot of effort that can just go to waste if Apple decides to just remove your app from the store one day without any justification whatsoever.